Methods and apparatus for a fiber optic display screen having an adjustable size

ABSTRACT

Methods and apparatus for a fiber optic display screen of adjustable size. In one embodiment, a screen comprises: a plurality of pixels formed by a terminal end of at least one optical fiber, wherein the pixels are substantially equidistant from each other along a first axis in a first screen size and in a second screen size that is larger than the first size.

BACKGROUND

As is known in the art, large electronic displays are components ofmodern information technology systems, particularly for outdoor displayapplications. These displays range from large televisions based onvarious technologies, e.g., plasma, LCD (Liquid Crystal Display), LED(Light Emitting Diodes), etc., to projection systems and LED screens.While these systems are deployed extensively, they generally requirerobust, heavy platforms to support their weight. Such systems can alsorequire extensive cooling systems that drive up costs and limit theirdeployment on weight-sensitive platforms like aerostats, balloons,blimps and other aircraft. In addition, conventional displays aredesigned for optimal viewing at a fixed distance and angle and do notpermit real time adjustments in optimal viewing distance to accommodatea change in the viewing distance of the display caused either by movingthe platform closer to the viewer or the viewer moving closer to theplatform. Also, deployment of such systems on billboard platforms,buildings and other venues often requires redesign or robust mountingplatforms to accommodate added mass.

Fiber optic displays have also been developed which can mitigate some ofthese challenges, but are dependent on precisely ordering fibers, whichis a difficult and costly process. U.S. Pat. No. 6,571,043 to Lowry etal. discloses a large screen fiber optic display and a method tomanufacture displays. U.S. Pat. Nos. 5,327,514 and 5,515,470 disclosemethods for projecting coherent images through incoherent fiber opticbundles and are incorporated herein by reference.

Prior attempts to address weight issues for large display systemsinclude screens formed from light emitting diodes (LEDs). However, thesesystems have significant weight limitations due to the need for coupledcooling and electrical power.

SUMMARY

Exemplary embodiments of the invention provide methods and apparatus fora large screen fiber optic display having high fiber count. Whileexemplary embodiments of the invention are shown and described inconjunction with particular applications, such as aerial displays, it isunderstood that exemplary embodiments of the invention are applicable todisplay systems in general in which relatively large displays aredesirable.

In one aspect of the invention, a fiber optic display screen comprises:a plurality of pixels formed by a terminal end of at least one opticalfiber, wherein the pixels are substantially equidistant from each otheralong a first axis in a first screen size and in a second screen sizethat is larger than the first size.

The screen can further include one or more of the following features:the pixels are substantially equidistant from each other along a secondaxis in a first screen size and in a second screen size that is largerthan the first size such that an aspect ratio of the screen is the samefor the first and second screen sizes, terminal blocks to support eachof the pixels, elastic bodies connecting adjacent ones of the terminalblocks, the elastic bodies bias the pixels to equidistant locations,interconnected modules to support the pixels, the interconnected modulesinclude guides, each of the pixels comprises multiple optical fiberterminal ends, the screen can provide different content at differentviewing angles, the screen is not physically connected to a laser sourcefor generating images for the screen, a free space coupler to receivelight from the laser source via air, and/or an aerial vehicle, whereinthe screen is secured to the aerial vehicle.

In another aspect of the invention, a method comprises: employing afiber optic display screen having a plurality of pixels formed by aterminal end of at least one optical fiber, and transitioning the screenfrom a first size to a second size that is larger than the first size,wherein the pixels are substantially equidistant from each other in thefirst screen size and in the second screen size, utilizing elasticbodies to space the pixels equidistantly, using terminal blocks tosupport each of the pixels, forming each of the pixels from multipleoptical fiber terminal ends, providing different content from the screenat different viewing angles, locating the screen remotely from a lasersource to generate images for the screen, wherein there is no physicalconnection between the screen and the laser source, using a free spacecoupler to receive light from the laser source via air, and/or securingthe screen to an aerial vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of this invention, as well as the inventionitself, may be more fully understood from the following description ofthe drawings in which:

FIG. 1 is a pictorial representation of a display system having a fiberoptic display screen coupled to a remote laser system;

FIG. 2 is a schematic representation showing further detail for thesystem of FIG. 1;

FIG. 3 is a block diagram showing further detail for the systems ofFIGS. 1 and 2;

FIG. 3A is a schematic representation of a micro-lens array that canform a part of the system of FIG. 1;

FIG. 4 is a schematic representation of a display system having anuntethered vehicle with a free space coupler;

FIG. 4A is a schematic representation showing further detail for thesystem of FIG. 4;

FIG. 4B is a schematic representation showing further detail for analternative embodiment of a coupler;

FIG. 5 is a schematic representation of a reflecting coupler that canform a part of the system of FIG. 4;

FIG. 5A is a schematic representation of a center cube prism that canform a part of the system of FIG. 4;

FIGS. 6A and 6B are pictorial representations of a display screen thatis adjustable in size;

FIG. 6C is a schematic representation showing screen pixel blockscoupled by elastic bodies;

FIG. 6D is a schematic representation showing screen pixel blockscoupled by elastic bodies having different spring constants;

FIG. 7 is a schematic representation showing a screen withinterconnected modules;

FIGS. 7A and 7B are respective top and side view of a module in FIG. 7;

FIG. 8A is a schematic representation of a system to map an unorderedfiber bundle;

FIG. 8B is a pictorial representation of an unordered fiber bundle andan ordered fiber bundle coupled to a display screen;

FIG. 9 is a pictorial representation of a pixel having multiple fibers;

FIG. 9A is a pictorial representation of the resolvable area of thehuman eye;

FIG. 9B is a pictorial representation of a multi-fiber, multi-channelpixel;

FIG. 10 is a schematic representation of fibers cleaved at differentangles;

FIG. 11 is pictorial representation of viewing angles for differentfiber cleave angles;

FIG. 12 is a schematic representation of a six-round-one fiber bundle;

DETAILED DESCRIPTION

FIG. 1 shows an exemplary display system 10 having a display screen 12on an aerostat 14 in accordance with exemplary embodiments of theinvention. In general, the relatively heavy components associated withgenerating the image on the display screen 12 are on the ground. In anexemplary embodiment, the aerostat 14 is tethered to a ground station 18by a cable 16, which includes high power optical fibers to carry theillumination to a pixelator, for transmitting an image to the displayscreen 12. The terminal ends of a fiber optic bundle provide the lightsource for the display screen.

While the display screen is shown secured to an aerostat, it isunderstood that the screen can be supported by any vehicle, vessel,aircraft, helicopter, platform, building, and the like, to enable usersto view images on the screen.

FIGS. 2 and 3 show further detail for the display system 10 of FIG. 1.The display system 10 includes a screen 102 to display imagestransmitted from a DLP (digital light processing) system 104 via pixelfibers 103. In general, the relatively heavy components, such as lasers108, power circuitry 110, etc., associated with generating the imagesare decoupled from the display screen 102. In exemplary embodiments, thelaser and associated equipment is ground-based. With this arrangement,display screens 102 can be deployed on weight-limited platforms, such asbuildings, billboards, aerostats, balloons, blimps, and the like.

Light from the laser source(s) 108 is coupled into a high-power-densityfiber-optic 105 relay, the distal end of which is coupled usingcondenser optics 106 to the digital pixelator 104, such as a DLP chip.The image formed by the pixelator 104 is then relayed with image relayoptics to a fiber optic bundle 103. It is understood that the terminalends of the fibers 103 represent the pixels of the display 102.

FIG. 3A shows an exemplary micro-lens array 150 to receive light fromthe DLP unit 152 for transmission into the fiber bundle 154. Fiber toDLP to fiber is known in the art as has been used in telecommunicationrouting technology, as disclosed for example, in “High-yield FabricationMethods for MEMS Tilt Mirror Array for Optical Switches,” by J.Yamaguchi et al, NTT Technical Review, 2010. Micro-lens arrays are wellknown to one of ordinary skill in the art, as well as their use tocouple fiber arrays. Air gaps in the fiber bundle can be removed fromthe fiber optic bundles in a variety of ways known to one of ordinaryskill in the art, such as by using heated drawing as described in U.S.Pat. No. 5,222,188 “Polymer optical fiber bundle and method of makingthe same.”

With this arrangement, the condenser 106, pixelator 104, andbundle/display 102 can be located a significant distance from theoptical source 108. For example, commercially available fibers haveattenuation of only a few decibels per kilometer, making efficienttransmission trivial over several hundreds of meters.

FIGS. 4 and 4A show a further embodiment of a display system 200 inwhich free space coupling is used to replace the high power fiber opticsof the fiber optic source relay. As used herein, free space couplingrefers to transmitting high intensity light and or image informationthrough the air. FIGS. 5 and 5A show an exemplary retro reflectingcoupler 210 having reflector guides 250 and a rear aperture 215 toreceive the reflected light. By eliminating a physical connection fromsource to display, i.e., a physically decoupling from the optical powersource, the display system weight is significantly reduced. In theillustrated embodiment, an aerostat 220 supports the retro reflectingcoupler 210.

In one embodiment shown in FIGS. 4-5A, a laser source 202 is coupledinto a displaced fiber optic coupler 210 that is subject to rotation anddisplacement, such as by wind, forward movement, etc. Feedback from thecoupler 210 is used to automatically adjust for both displacement androtation, as described below.

The laser beam output is directed through a reflective plate 220 with acentral aperture 221, transmitted through a first dichroic mirror 209,and then reflected from an adjustable mirror 208 towards the fiber lasercoupling unit 210. As is known in the art, a dichroic mirror refers to aglass surface coated with a film that reflects certain colors of lightwhile allowing others to pass through. The beam received by the coupler210 is transmitted through a corner-cube prism 213 having, instead of anapex, a rear face/aperture 215. The majority of the beam exits the rearaperture 215 and passes through a second dichroic mirror 211 to apartial beam splitter 225. A small portion of the incident beam isretro-reflected from the modified corner cube prism 210 in a directionnormal to the incident beam. The portion of the beam reflected from thepartial beamsplitter 225 is incident on a first quad detector 227. Theremainder of the beam transmitted through the rear aperture 215 iscoupled into a fiber 219 in a conventional manner. Concurrently, aninfrared beam carrying image data from a first transceiver unit 207 isreflected off of the first dichroic mirror 209 and is coaxial with thelaser beam. The infrared beam is reflected off of adjustable mirror 208,transmitted through corner cube prism 213, reflected off of the seconddichroic mirror 211 and received by a second transceiver unit 212. Thecoupler 210 comprises a common rigid mounting body such that the unitmoves as a single unit, which simplifies alignment.

The retro-reflected beam is reflected off the adjustable mirror 208 andis reflected off the reflector 220 with the central aperture and onto asecond quad detector 229.

By providing transmission through the aperture 215, the receivingassembly can track the source. In this way the source assembly tracksand orients to the receiver and the receiver tracks and orients to thesource. While the source and receiver tracking is similar, it isunderstood that the source uses an adjustable mirror while the receiveruses an adjustable assembly. i.e., cornercube, fiber coupler, beamsplitter, etc.

Data from the first quad detector 227 is used as feedback to adjust theangle of the coupler unit 210 such that the corner cube primary facet217 is roughly normal to the incident beam from the minor 208.Similarly, data from the second quad detector 229 is used as feedback toadjust the angle of the adjustable mirror 208 such that it directs thebeam into the center of the corner cube primary facet 217. In this way,both the angle and displacement are corrected for automatically.

It is understood that further embodiments can be directed to a varietyof applications, such as free space communication, such as infraredfree-space telecommunication and radio-frequency communications.

It is understood that the coupler 210 can have a variety ofconfigurations to meet the needs of a particular application. In theillustrated embodiment, for coupler 210, the incident beam propagatesfrom the adjustable mirror 208 to the face of the cornercube 213 througha distance of free space. For illustrative purposes a Gaussian beam ofred light (700 nm) with a beam waist of 5 mm that is transmitted 100meters will have substantially all its energy contained in a diameter of7 cm. Therefore, the rear aperture 215 of the coupler should have aclear aperture of about this diameter. Similarly, the clear aperture ofthe first facet 217 only needs to extend slightly beyond this diameter,e.g., a few centimeters, for small angular variations that would beexperienced during use.

In one embodiment, the corner cube is a prism formed from glass. In analternative embodiment, corner cube reflector has three reflectivesurfaces. In one embodiment, the rear aperture 215 is formed by cuttingan elliptical section out of each of the three reflectors to create acircular aperture when viewed along the optical axis, as shown in FIG.4B. This configuration increases the feedback signal with smallmisalignments of the coupler. The surfaces of the corner cube reflectorcan be formed from protected aluminum or other known highly reflectivematerial across the transmitted wavelengths.

It is understood that image data can be transmitted via radio frequency,or other means known in the art instead of via the infrared transceiversystem comprising transceiver unit 207, transceiver unit 212, firstdichroic mirror 209 and second dichroic mirror 211.

It is understood that the adjustable mirror 208 can be provided from avariety of known mount systems. Exemplary commercially availableelectronically driven kinematic mirror mounts are provided by Thorlabsof Newton, N.J. A piezoelectric driven drive has angular resolution ofless than 0.1 arcseconds, corresponding to linear displacements andresolution of less than 1 cm at distanced greater than 100 meters.Similarly, these drives orient at speeds in excess of 10 degrees persecond, corresponding to approximately 20 meters per second platformspeed.

In another aspect of the invention shown in FIGS. 6A and 6B, a displaysystem 300 includes a fiber optic display screen 302 that can modifypixel 304 spacing. With this arrangement, the screen 302 can adapt toprovide optimal viewing quality at a differing viewer distances. Forexample, a display screen on an aerostat can dynamically alter interpixel 304 spacing based upon how far away viewers are located. As can beseen, FIG. 6A shows the screen 302 having a first size and FIG. 6B showsthe screen 302 having a second size that is larger than the first size.Exemplary images are show alongside the screen. As the screen 302expands, the pixels 304 move apart uniformly.

In an exemplary embodiment, the fiber optic pixels are embedded in thescreen 302, which is formed from an elastic material. In one embodiment,the material is flexible in at least two dimensions, e.g., x and y axes.It is understood that both the x and y axes of the display can bechanged independently, thus altering the aspect ratio of the screen. Inthat case, equal pixel spacing occurs along each of those axes. That is,the pixels can move along the x axis, the y axis, or both axes to retainor alter the aspect ratio of the screen.

In one embodiment, an adjustable screen includes a set of pixelscomprising a fiber termination mounted in a termination ‘block’. A pixelblock is connected to each adjacent block with at least one elasticbody, such as a rubber band. With this arrangement, pixels willautomatically tend to be equally spaced by virtue of Hook's law.

In order to counter the effects of gravity and ensure equal spacing inthe vertical direction, spring constants of the elastic bodies (ornumber of elastic bodies) will vary by row because each row of pixelscarries the sum of the mass of the pixels beneath it. In one embodiment,the elastic bodies have increasing spring constants. In an alternativeembodiment, elastic bodies are added at each connection. In a furtherembodiment, a monolithic material is used in which the material stretchdecreases in a gradient along the vertical axis.

FIG. 6C shows a front view of a single pixel column having a bottompixel BP connected to second pixel SP with one elastic body EB1, and athird pixel TP connected to the second pixel SP by two elastic bodiesEB2. A fourth pixel FP is coupled by three elastic bodies EB3. Thisarrangement maintains equal spacing in the vertical axis. FIG. 6D showsa bottom pixel BP connected to a second pixel SP with a first elasticbody EB1, a third pixel TP connected to the second pixel SP by a secondelastic body EB2 having a spring constant greater, e.g., about twice aslarge, than a spring constant of the first elastic body EB1 to maintainequal spacing in the vertical axis. Each pixel is connected with arespective elastic body having a spring constant to maintain pixelspacing in the vertical axis.

To optimize the screen for a selected distance, in one embodiment, thescreen is pulled from the edges at the same rate in the x and y axes tostretch the screen into a larger size. By controllably releasing thescreen edges, the screen can return to a smaller size.

In general, the change in pixel spacing should be uniform across thedisplay. That is, a change in screen size should move neighboring pixelsin the center of the screen the same distance as neighboring pixels onan edge of the screen, and so on.

Exemplary materials for the screen include elastic threads, elasticcords, and other discrete elastic bodies well known to one of ordinaryskill in the art.

FIGS. 7-7B show an exemplary system 400 to maintain uniformpixel-to-pixel spacing in the display as the screen size changes. Thesystem 400 includes a series of interconnected modules 402-a-N on whichpixels 404 are mounted to form a lattice assembly. The modules 402 areinterconnected by guides 406 and/or elastic spacers 408. In theillustrated embodiment, the guides enable movement of modules along therespective x and y axes. The guides 406 enable the modules 402 to movealong the tracks for maintaining proper directional alignment. Thespacers 408 can calibrate pixel spacing.

In a further aspect of the invention shown in FIGS. 8A and 8B, anoptical fiber arrangement for a display is provided in which fiberplacement in the screen does not need to be precisely coordinated withthe fiber arrangement in the distal end of the fiber bundle. Thiseliminates the need for a coherent fiber bundle and instead allows fiberscreens to be provided without the need to coordinate the fiber-bundletip and screen-pixel geometries.

FIG. 8A shows a system 500 to map an unordered fiber bundle. A computer502 controls information to a digital projector 504. A mapping matrixcan be determined by sequentially transmitting optical signals from adigital relay projector 504 into corresponding fibers of the bundlematrix 506 in a known order. Simultaneously, the screen output 510 fromthe corresponding fibers is monitored by a detector 508, such as ahigh-resolution digital camera. By transmitting sequentially through allthe bundle matrix inputs and monitoring the corresponding outputlocations, a map is created to identify which digital relay projectorelement corresponds to each pixel of screen output. For example, digitalprojector element PEn corresponds to fiber bundle matrix element En,which subsequently maps to pixel Pn.

Digital media is subsequently reordered by applying this map in reverse.For example, data element DEm is reordered to be element Em. Thereordered data is subsequently transmitted through the digital projector504 and the screen output 510 now corresponds to a high-fidelityreproduction of the original data set.

With this arrangement, coherent images are produced by a particular dataflow. More particularly, a coherent image is generated and encoded usinga using a mapping function. The encoded image is projected into a fiberbundle. A display of the decoded image is generated at the distal end ofthe incoherent bundle.

In the prior art, such as U.S. Pat. No. 5,515,470, a map, whichcorrelates two ends of an incoherent fiber bundle but does encodedigital media, decode the media with an incoherent fiber bundle, andthen display the content of the digital media. The '470 patent disclosesthe creation of a pixel map that is used to decode image datatransmitted through an incoherent bundle. The data flow generating animage of an object, using an incoherent fiber bundle to encode theimage, capturing the encoded image by a camera, applying a mappingfunction to the camera data, and decoding the image for display.

FIG. 8B shows an ordered fiber bundle OFB and an unordered fiber bundleUFB to transmit data from the input of the fiber bundle to the displayscreen.

In another aspect of the invention, multiplexed visual content ispresented to an observer using a fiber optics screen, where each pixelelement is capable of transmitting multiple content streams. With thisarrangement, different information can be provided to people atdifferent viewing angles with respect to the screen, for example.

FIG. 9 shows a pixel 900 having multiple fibers 902 a-e. In oneembodiment, the multi-fiber pixel has a size that is less than theresolvable area of the human eye shown in FIG. 9A. FIG. 9B shows amulti-fiber, multi-channel pixel, where each fiber carries differentinformation.

In one embodiment shown in FIG. 10, the fibers 912 a-d are cleaved atdiscrete and known angles A1-4 and packaged into a pixel bundle. In thisway, a single pixel can have multiplexed content that varies by viewingangle. For example, a common multimode silicate optical fiber has anumerical aperture of roughly 0.22. A fiber that is cleaved normal tothe length of the fiber has a symmetrical emission viewing angle ofabout 25 degrees (ranging from −12.7 to +12.7 degrees). Similarly, afiber with a cleave angle of 10 degrees also has a viewing angle ofabout 25 degrees but ranges from 2 to 27 degrees. In the extreme case, afiber which is cleaved such that rays of light hit the cleave facet atangles greater than the critical angle are reflected from the facet anddirected out the side of the fiber, a so called side-firing geometry asshown in fiber 912 d at angle A4. Therefore, a set of sevenfibers—cleaved at −55, −31, −15, 0, 15, 30, and 55 degrees can be usedto cover the entire azimuth viewing range of 180 degrees and can deliverdiscrete viewing content to up to seven directions. FIG. 11 showsvariation in fiber output angle as determined by the fiber cleave usinga multimode silicate fiber with an NA of 0.22 and a flat facet cleave.

It is understood that fiber cleaving into a relatively narrow angleenables more efficient delivery of optical energy to the audience. Thiscan be a factor in weight, size, cost reductions and improved audienceexperience.

In one embodiment shown in FIG. 12, seven fibers F1-F7 can be arrangedin a six-around-one geometry. A bundle of multimode optical fibers inthis geometry can have a diameter less than one millimeter. As the humaneye has angular resolution of roughly one minute of arc, the sourcefiber would be indistinguishable at any realistic viewing distance wherethey eye has focal power, e.g., greater than a few centimeters.

With this arrangement, a multi-fiber pixel can be used to directdifferent content to different sections of a viewing audience. Forexample, if a display is part of a stadium size screen, playback of liveaction can be tailored to give a different view than what theyexperienced live or a similar view. Additionally, the multi-fiber pixelscan inform different sections about different emergency exitinstructions. Further, multi-fiber pixels can be used to overcome thechallenges of parallax with viewing angle. For example, audience membersat large angles to the screen would not see a distorted “scrunched”image, but rather, see content with an appropriate aspect ratio. Also,control over the range of viewing angles for a display is useful fordaytime or low-power viewing. Exemplary embodiments of directionaloutput pixels can concentrate the output power of the screen only to theappropriate audience.

In an alternative embodiment, any single fiber could be apolarization-maintaining fiber for carrying polarized data and could beused to stream three dimensional data compatible with modern 3Darchitectures.

It is understood that any practical number of fibers can be used to forma pixel. It is further understood that any practical number of cleavingconfigurations for various fiber types can be used to form a desirednumber of viewing angles for respective channels with various viewingangles sizes based for the selected fiber type.

Having described exemplary embodiments of the invention, it will nowbecome apparent to one of ordinary skill in the art that otherembodiments incorporating their concepts may also be used. Theembodiments contained herein should not be limited to disclosedembodiments but rather should be limited only by the spirit and scope ofthe appended claims. All publications and references cited herein areexpressly incorporated herein by reference in their entirety.

1. A fiber optic display screen, comprising: a plurality of pixelsformed by a terminal end of at least one optical fiber, wherein thepixels are substantially equidistant from each other along a first axisin a first screen size and in a second screen size that is larger thanthe first size.
 2. The screen according to claim 1, wherein the pixelsare substantially equidistant from each other along a second axis in afirst screen size and in a second screen size that is larger than thefirst size such that an aspect ratio of the screen is the same for thefirst and second screen sizes.
 3. The screen according to claim 1,further including terminal blocks to support each of the pixels.
 4. Thescreen according to claim 3, further including elastic bodies connectingadjacent ones of the terminal blocks.
 5. The screen according to claim4, wherein the elastic bodies bias the pixels to equidistant locations.6. The screen according to claim 1, further including interconnectedmodules to support the pixels.
 7. The screen according to claim 6,wherein the interconnected modules include guides.
 8. The screenaccording to claim 1, wherein each of the pixels comprises multipleoptical fiber terminal ends.
 9. The screen according to claim 8, whereinthe screen can provide different content at different viewing angles.10. The system according to claim 1, wherein the screen is notphysically connected to a laser source for generating images for thescreen.
 11. The system according to claim 10, further including a freespace coupler to receive light from the laser source via air.
 12. Thesystem according to claim 10, further including an aerostat, wherein thescreen is secured to the aerial vehicle.
 13. A method, comprising:employing a fiber optic display screen having a plurality of pixelsformed by a terminal end of at least one optical fiber; andtransitioning the screen from a first size to a second size that islarger than the first size, wherein the pixels are substantiallyequidistant from each other in the first screen size and in the secondscreen size.
 14. The method according to claim 13, further includingutilizing elastic bodies to space the pixels equidistantly.
 15. Themethod according to claim 13, further including using terminal blocks tosupport each of the pixels.
 16. The method according to claim 13,further including forming each of the pixels from multiple optical fiberterminal ends.
 17. The method according to claim 16, further includingproviding different content from the screen at different viewing angles.18. The method according to claim 13, further including locating thescreen remotely from a laser source to generate images for the screen,wherein there is no physical connection between the screen and the lasersource.
 19. The method according to claim 18, further including using afree space coupler to receive light from the laser source via air. 20.The method according to claim 18, further including securing the screento an aerostat.